DNA molecules exchange parts with each other in a variety of circumstances. In meiosis eukaryotic chromosomes break and join parts with strict adherance to homology, so that the order of gene loci is preserved. This process, generalized genetic recombination, will be investigated in the eukaryote Saccharomyces cerevisiae and in the bacteriophage Lambda. A fuller understanding of recombination may have implications for developmental anomalies, immune deficiencies, and cancer induction. The proposed invesitagations will seek and characterize nucleotide sequences that play special roles in recombination. These studies will include tests of hypotheses regarding the mechanism of action of the Chi sequence (5 feet GCTGGTGG). Recombination can be initiated by doulbe stand breaks in DNA. It is possible that such breaks are the normal mode of initiation in meiosis. That hypothesis will be tested as will hypotheses regarding the involvement of double stand breaks in prokaryotic recombination. In addition, improvements in gene cloning methodology will be attempted. The improved methods sought are in vitro packaging of Lambda DNA and in the cloning of DNA palindromes.